Fusion Nuclear Science and Technology (FNST) Challenges and Facilities
on the Pathway to Fusion Energy
Mohamed Abdou Distinguished Professor of Engineering and Applied Science (UCLA) Director, Fusion Science and Technology Center (UCLA)Founding President, Council of Energy Research and Education Leaders, CEREL (USA)
With input from the FNST Community
Related publications can be found at www.fusion.ucla.edu
Remarks at the FPA Meeting ● Washington DC ● December 14-15, 2011 1
Over the past 3 decades we have done much planning and defining ambitious goals for the long term (power reactors) based on what we “perceive” the technical challenges are, and what may be attractive.
– This planning has suffered from lack of fundamental knowledge on FNST
• NOW it is time to focus on “actions” to perform substantial FNST R&D in the immediate and near-term futures: this will give us real scientific and engineering data with which we can:
– evaluate our long-term goals (too ambitious? Realistic?)– define a practical and credible pathway
The Major Challenges NOW are in FNST
The major FNST challenges are not only the difficulty and complexity of the technical issues
But also how and where (facilities) we can do experiments to resolve these issues.
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FNST is the science, engineering, technology and materials for the fusion nuclear components that
generate, control and utilize neutrons, energetic particles & tritium.
Fusion Nuclear Science & Technology (FNST)
The nuclear environment also affects Tritium Fuel Cycle Instrumentation & Control Systems Remote Maintenance Components Heat Transport &
Power Conversion Systems
In-vessel Components Plasma Facing Components
divertor, limiter, heating/fueling and final optics, etc.
Blanket and Integral First Wall Vacuum Vessel and Shield
These are the FNST Core for IFE & MFE
Exhaust Processing
PFCsBlanket
T storage & management
Fueling system
DT plasma
T waste treatment
Impurity separation,Isotope separation
PFC & Blanket T processing
design dependent
optics
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Fusion Nuclear Science and Technology (FNST) must be the Central element of any Roadmapping for fusion
ITER (and KSTAR, EAST, JT-60SU, etc) will show the Scientific and Engineering Feasibility of:– Plasma (Confinement/Burn, CD/Steady State, Disruption control, edge control)– Plasma Support Systems (e.g. Superconducting Magnets)
• ITER does not address FNST (all components inside the vacuum vessel are NOT DEMO relevant - not materials, not design, not temperature)
(TBM provides very important information, but limited scope)
• FNST is the major missing Pillar of Fusion Development
FNST will Pace Fusion Development Toward a DEMO.
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What are the Principal Challenges in the development of FNST?
The Fusion Nuclear Environment• Multiple field environment (neutrons, heat/particle fluxes, magnetic
field, etc.) with high magnitude and steep gradients.• Nuclear heating in a large volume with sharp gradients
0 drives most FNST phenomena.0 But simulation of this nuclear heating can be done only in DT-plasma
based facility.
Challenging Consequences• Non-fusion facilities (laboratory experiments) need to be substantial to
simulate multiple fields, multiple effects0 We must “invest” in new substantial laboratory-scale facilities.
• Results from non-fusion facilities will be limited and will not fully resolve key technical issues. A DT-plasma based facility is required to perform “multiple effects” and “integrated” fusion nuclear science experiments. So, the first phase of FNSF is for “scientific feasibility”.
• But we have not yet built DT facility – so, the first FNSF is a challenge.5
Neutrons (flux, spectrum, gradients, pulses)- Radiation Effects - Tritium Production- Bulk Heating - Activation and Decay Heat
Combined Loads, Multiple Environmental Effects
- Thermal-chemical-mechanical-electrical-magnetic-nuclearinteractions and synergistic effects
- Interactions among physical elements of components
Magnetic Fields (3-components, gradients)- Steady and Time-Varying Field
Mechanical Forces- Normal (steady, cyclic) and Off-Normal (pulsed)
Heat Sources (thermal gradients, pulses)- Bulk (neutrons) - Surface (particles, radiation)
Particle/Debris Fluxes (energy, density, gradients)
Fusion Nuclear Environment is Complex & Unique
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Non-fusion facilities (Laboratory experiments) need to be substantial to simulate multiple effects Simulating nuclear bulk heating in a large volume is the most difficult and is most needed Most phenomena are temperature (and neutron-spectrum) dependent– it needs DT fusion facility The full fusion Nuclear Environment can be simulated only in DT plasma–based facility
......
......
......
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...
Volumetric Heating
0.0 100
5.0 10-9
1.0 10-8
1.5 10-8
2.0 10-8
2.5 10-8
3.0 10-8
0 5 10 15 20 25 30
Tri
tiu
m P
rod
uct
ion
Ra
te (
kg
/m3 .s
)
Radial Distance from FW (cm)
Radial Distribution of Tritium Production in LiPb Breeder
Neutron Wall Loading 0.78 MW/m2
DCLL TBM LiPb/He/FS
90% Li-6
Front Channel Back Channel
10-1
100
101
102
103
0 5 10 15 20 25 30 35 40
dpa/FPYHe appm/FPYH appm/FPY
Dam
age
Rat
e in
Ste
el S
tru
ctu
re p
er F
PY
Depth in Blanket (cm)
Radial Distribution of Damage Rate in Steel Structure
Neutron Wall Loading 0.78 MW/m2
DCLL TBMLiPb/He/FS
90% Li-6
These gradients play a major role in the behavior of fusion nuclear components.They can be simulated only in DT plasma-based facility.
There are strong GRADIENTS in the multi-component fields of the fusion environment
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Tritium
(for ST)
Magnetic Field
Radial variation of tritium production rate in PbLi in DCLL
Damage parameters in ferritic steel structure (DCLL)
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Simulating nuclear bulk heating in a large volume with gradients is Necessary to:1. Simulate the temperature and temperature gradients
* Most phenomena are temperature dependent* Gradients play a key role, e.g. :
– temperature gradient, stress gradient, differential swelling impact on behavior of component, failure modes
2. Observe key phenomena (and “discover” new phenomena)– e.g. nuclear heating and magnetic fields with gradients result in complex mixed convection with
Buoyancy forces playing a key role in MHD heat, mass, and momentum transfer– for liquid surface divertor the gradient in the normal field has large impact on fluid flow behavior
Simulating nuclear bulk heating (magnitude and gradient) in a large volume requires a neutron field - can be achieved ONLY in DT-plasma-based facility
– not possible in laboratory– not possible with accelerator-based neutron sources– not possible in fission reactors ( very limited testing volume, wrong spectrum, wrong
gradient)
Conclusions: – Fusion development requires a DT-plasma based facility FNSF to provide the
environment for fusion nuclear science experiments.– The “first phase” of FNSF must be focused on “Scientific Feasibility and Discovery” –
it cannot be for “validation”.
Importance of Bulk Heating and Gradients of the fusion nuclear environment
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CHALLENGE we must face in fusion development
Conclusions:
1- The Primary Goal of the next step, FNSF (or at least the first stage of FNSF) is to provide the environment for fusion nuclear science experiments.
Trying to skip this “phase” of FNSF is like if we had tried to skip all plasma devices built around the world (JET, TFTR, DIII-D, JT-60, KSTAR, EAST, ,etc) and go directly to ITER (or skipping ITER and go directly to DEMO).
2- The next step, FNSF (or at least the first stage of FNSF) cannot be overly ambitious although we must accept risks. The DD phase of the first FNSF also plays key testing role in verifying the performance of divertor, FW/Blanket and other PFC before proceeding to the DT phase.
Since the integrated fusion environment, particularly volumetric nuclear heating (with gradients) can be realized only in a DT-Plasma Based Facility:
Then we will have to build the nuclear components in the first DT plasma-based device (first FNSF) from the same technology and materials we are testing:
– WITH ONLY LIMITED data from single-effect tests and some multiple-effect tests– Without data from single-effect and multiple-effect tests that involve Volumetric Nuclear
Heating and its gradient– Without data from synergistic effects experiments
Component Number
Failure rate in hr-1
MTBF in years
MTTR for Major failure, hr
MTTR for Minor failure, hr
Fraction of failures that are Major
Outage Risk Component Availability
Toroidal Coils
16 5 x10-6 23 104 240 0.1 0.098 0.91
Poloidal Coils
8 5 x10-6 23 5x103 240 0.1 0.025 0.97
Magnet supplies
4 1 x10-4 1.14 72 10 0.1 0.007 0.99
Cryogenics 2 2 x10-4 0.57 300 24 0.1 0.022 0.978
Blanket 100 1 x10-5 11.4 800 100 0.05 0.135 0.881
Divertor 32 2 x10-5 5.7 500 200 0.1 0.147 0.871
Htg/CD 4 2 x10-4 0.57 500 20 0.3 0.131 0.884
Fueling 1 3 x10-5 3.8 72 -- 1.0 0.002 0.998
Tritium System
1 1 x10-4 1.14 180 24 0.1 0.005 0.995
Vacuum 3 5 x10-5 2.28 72 6 0.1 0.002 0.998
Conventional equipment- instrumentation, cooling, turbines, electrical plant --- 0.05 0.952
TOTAL SYSTEM 0.624 0.615
Availability required for each component needs to be high
DEMO availability of 50% requires: Blanket/Divertor Availability ~ 87% Blanket MTBF >11 yearsMTTR < 2 weeks
Component # failure MTBF MTTR/type Fraction Outage Component rate Major Minor Failures Risk Availability (1/hr) (yrs) (hrs) (hrs) Major
MTBF – Mean time between failuresMTTR – Mean time to repair
Two key parameters:
Reliability/Availability/Maintainability/Inspectability(RAMI) is a Serious Issue for Fusion Development (table from Sheffield et al)
Extrapolation from other technologies shows expected MTBF for fusion blankets/divertor is as short as ~hours/days, and MTTR ~months
GRAND Challenge: Huge difference between Required and Expected!!
(Due to unscheduled maintenances)
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Carefully studying these FNST challenges
lead to suggesting that we should plan on
FNSF as the “Now + 1” (or “0+1”) facility.
Not as “DEMO-1” facility.
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D E M OPreparatory R&D
Science-Based Pathway to DEMO Must Account for Unexpected FNST Challenges in Current FNST and Plasma Confinement Concepts
Scientific FeasibilityAnd Discovery
Engineering Feasibility and
Validation
Engineering Development
• Today, we do not know whether one facility will be sufficient to show scientific feasibility, engineering feasibility, and carry out engineering development
OR if we will need two or more consecutive facilities. May be multiple FNSF in parallel?!
We will not know until we build one!! • Only Laws of nature will tell us regardless of how creative we are. We may even find
we must change “direction” (e.g. New Confinement Scheme)
Non-Fusion Facilities
Fusion Facility(ies)
FNSF
ORFNSF-1FNSF-2
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I IIIII
Testing in the Integrated Fusion Environment (100-1000’sM)Functional tests: ITER TBM Experiments and PIE
Engineering Feasibility Testing in a Fusion Nuclear Science Facility
Multi-Effect Test Facilities (each ~5-20M class)Blanket Mockup Thermomechanical/ Thermofluid Testing Facility
Tritium Fuel Cycle Development Facility Bred Tritium Extraction Testing Facility
Fission Irradiation Effects Testing on Blanket Mockups and Unit Cells
Fundamental Research Thrusts (each ~1-3M per year)PbLi Based Blanket Flow, Heat Transfer, and Transport Processes
Plasma Exhaust and Blanket Effluent Tritium Processing Helium Cooling and Reliability of High Heat Flux Surfaces /Blanket/FW
Ceramic Breeder Thermomechanics and Tritium ReleaseStructural and Functional Materials FabricationFN
ST P
yram
id
Establish the base of the pyramid Before proceeding to the top
We need substantial NEW Laboratory-scale facilities NOW
Concluding Remarks• Launching an aggressive FNST R&D program now is essential to
defining “informed” vision and “credible” pathway to fusion energy.
Most Important Steps To Do Now1. Substantially expand exploratory R&D
– Experiments and modeling that begin to use real materials, fluids, and explore multiple effects and synergistic phenomena
• Major upgrade and new substantial laboratory-scale facilities
• Theory and “FNST Simulation” project (parallel and eventually linked to “plasma simulation” project).
This is essential prior to any “integrated” tests (TBM, FNSF, etc.)
2. Move as fast as possible to “integrated tests” of fusion nuclear components – these can be performed only in DT plasma-based facility.
a) TBM in ITER
b) FNSF: Initiate studies to confront challenges with FNSF (think of “0+1” not “DEMO-1”).
– Address practical issues of building FNSF “in‐vessel” components of the same materials and technologies that are to be tested.
– Evaluate issues of facility configuration, maintenance, failure modes and rates, physics readiness (Quasi‐steady state? Q ~ 2‐3?). These issues are critical - some are generic while others vary with proposed FNSF facility.
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